135157537domain: NPropertiesPrimalityPrimeyesAppears in sequencesNumbers k such that k and the k-th triangular number T(k) = k*(k+1)/2 have only odd digits.at n=30A347475Least n-digit number k with only odd digits such that the k-th triangular number also has only odd digits.at n=8A349247Prime numbersat n=7653932